Depth-of-Field

The one question I get asked a lot as a photographer who takes plenty of photos which have a shallow depth of field (blurred background) as well as “bokeh” (“those circle circle things in the photo”) is how I “edit” the blur background and “bokeh” into my photos. Well, here’s my answer.

A shallow depth of field is achieved when a large aperture (small f- number) is used to take the photo. Note that the smaller the f-number, the larger the aperture and the shallower the depth of field and likewise the larger the f-number, a smaller aperture and a deeper depth of field (Example; A photo taken at f1.8 has a shallower depth of field compared to f2.8)

Aperture is not the only thing that plays a role in a pleasantly blurred background, or rather there is another factor that makes a different between a normal blurred background and a beautiful one. That factor is the distance between the camera and the subject. The closer the subject is to the camera, the shallower the depth of field is. Likewise when you are shooting further away from the subject, your depth of field deepens.

Shot with Canon 1200D with Canon 24-105 F4L. 1/250 sec, F4, ISO400

At this point in the article, some might be wondering if all I do is shoot photos using the said techniques about with kit lenses and without any other lens. As much as people tend to believe that photography is not about the gear but the person behind it and though I personally believe this too, it does come to a point where you reach the limit of your current lens, for most of us who are newly starting to dabble in photography, the trusty 18-55mm f3.5-5.6 or the 55-250 f3.5-5.6 and we start to think, how do portrait photographers out there seem to be getting spectacular background blur than us, even after applying the basic techniques of Depth of Field. For people who have an interest in shooting portraits or photos in general with just the subject in focus and everything else blurred and blended in to the background, this is where one gets introduced to the “drug”. The 50mm f1.8.

Why is a fixed focal lens such as the 50mm f1.8 the “drug” of getting super shallow depth of field you wonder? This is because of this lens ability to stop down to a wide aperture of f1.8. That’s roughly almost 2 times more light being let into the camera sensor and aperture wise also two times wider than a typical 18-55mm kit lens (Edit note: Double check) As a beginner, why the 50mm f1.8 though? If you were to google “f1.8 lenses” you would find a few other choices of different focal lengths which offer the same wide open aperture of f1.8. For starters, a focal length of 50mm is the equivalent to what the human eyes see. Secondly, it suits people who are just starting about to dabble in photography by being kind to the wallet. A brand new 50mm f1.8 for Canon DSLR’s costs around RM360-380 (About USD82) Thirdly, for the price you are paying for this lens, it offers decent bokeh and slightly better sharpness. Lastly, it is also a very compact and light lens which is no burden to carry about in the camera bag!

That’s all there is to my photos? Yes, the most important thing is to understand the basics of depth of field and then applying it to your photos and you are pretty much halfway to getting better background blur in your photos. The 50mm f1.8 would be a great addition after you’ve fully understood the concept of depth of field so that it’s maximum potential can be achieved.

Useful info: There are many types of camera formats, Micro four thirds, medium format, full frame and APS-C (crop frame), the most common being the APS-C (crop sensor) and full frame.There are lenses specifically made for full frame cameras and lenses made specially for crop frame cameras. Full frame lenses produced by the same camera company as that of one’s crop frame sensor body can also be mounted on APS-C cameras but do note that the focal distances are tighter compared to when mounted on a full frame body. For example, a 24-70mm lens made for full frame cameras would give you a focal distance of 24-70mm but this is not the same if the same lens is coupled to a crop frame camera body where its focal distance will be 38-112mm. Likewise, lenses made for crop frame cameras can also be mounted on to full frame camera bodies but there will be heavy vignetting around the edges of the image. Full frame lenses are normally sharper when mounted on a crop sensor body although aperture wise it is same.

To find the focal distance of a full frame lens when mounted on to a crop frame sensor camera, simply multiply the lens focal distance with the crop factor for the particular brand. Canon has a x1.6 crop factor while Nikon has a x1.5 crop factor. (Example: A Canon 50mm f1.2L USM lens is equivalent to a focal distance of 80mm when mounted on to a crop frame Canon camera)

To end this article, here are some of my photos taken with a variety of lenses to give you an example to refer to 😉